Transition-metal catalyzed synthesis of delta-hydroxy-gamma-lactones from bis(trimethylsilyl) ketene acetals and allylic acetates via gamma-unsaturated carboxylic acids. Comments on the formation of alpha-cyclopropyl carboxylic acids

摘要

Bis(trimethylsilyl)ketene acetals react with allylic acetates in the presence of Pd(0) complexes to give gamma -unsaturated carboxylic acids together with alpha -cyclopropyl carboxylic acids. The unsaturated acids can be converted catalytically to delta -hydroxy-gamma -lactones by the: H2O2/MTO system (methyltrioxorhenium) and to butenolides by Pd(II) catalyzed intramolecular cyclization reactions. The structure of two of these lactones has been established by X-ray analysis. The mechanism of the formation of the cyclopropanic acids will be discussed. (C) 2001 Elsevier Science B.V. All rights reserved. [References: 61]